Researchers reveal higher historic tortoiseshell trade numbers

By Dana Kobilinsky

Historic trade of critically endangered hawksbill sea
turtles (Eretmochelys
imbricata) may have caused declines nearly
six times greater than previously thought, according to new research.

The researchers said the historical global trade
patterns that they found also align with current unauthorized fishing
activities. “There’s a strong overlap between countries exporting turtles for
tortoiseshell and countries today that have high rates of illegal, unreported
and unregulated fishing,” said Emily Miller, an assistant research scientist at
the Monterey Bay Aquarium and lead author of the recent study published in Science Advances. “It’s likely related
to historical economic and political aspects of these trade networks that have
developed over time.”

In the study, the team first collected as much historical data on the hawksbill sea turtle trade that they could find. One co-author contributed Japanese customs records of tortoiseshell imports that had never been published before. Other co-authors then pored through all published sources on hawksbills and curated them into a database.

But the researchers ran into a problem because trade
records showed only how many kilograms of turtle scutes —the individual plates
that make up a turtle’s shell — were reported. “We wanted to know how many
turtles were killed to understand the impact on the global population,” Miller
said. Material from the scutes is often carved into items including sunglasses,
bracelets, guitar picks and combs.

The researchers were able to get stranded and seized
turtle specimens to derive relationships to convert the kilos of scutes into the
number of turtles actually killed.

They estimated that nearly 9 million turtles were
harvested over the 150 years they had recorded. “The previously published
estimate was approximately 1.2 million,” she said.

Miller said they came up with a larger number because
of the extra data they were able to get their hands on. But previous studies
also assumed only the largest individuals were the ones being sold. “Because we
were able to get a seized shipment that came into the U.S. in the modern era,
we were able to figure out it wasn’t just a few large individuals but many
smaller adults, subadult and juveniles,” she said.

Then, the team looked at how patterns of hawksbill
trade lined up with illegal and unreported fishing. There was a strong overlap
between the countries with high illegal, unreported, and unregulated (IUU)
fishing rates and the countries that were historically exporting
tortoiseshells, she said. “Poor governance in those areas and long-standing
trade networks drive these patterns,” she said.

Miller said this can inform management decisions
today. She suggests since there is such overlap, enforcement agencies should
train and cross-deputize officers to be able to handle both fishing and
wildlife trafficking cases.

Because this is global trade, Miller said it is an
international issue and international awareness will help contribute to
solutions.

For individuals, she suggests people be aware of what products they are purchasing when they’re vacationing in tropical regions and also paying attention to where their seafood is coming from.

Dana Kobilinsky is associate editor at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.